Polylactic acid resins have some features that polylactic acid resins are inexpensive because the polylactic acid resins are produced from L-lactic acid used as a raw material according to a fermentation method from sugars extracted from maize, potato or the like, that the raw materials are derived from plants from which the amount of carbon dioxide discharged is very small, and that the resins have the properties of being strongly rigid and highly transparent, so that the utilization of the polylactic acid resins is expected at present.
For example, it is reported in Patent Publication 1 that a polylactic acid is combined with a particular plasticizer, e.g. a succinic acid ester, and a particular crystal nucleating agent, e.g. an organic crystal nucleating agent, thereby promoting crystallization in thermoforming while maintaining transparency, whereby a molded article having excellent heat resistance or the like is obtained.
In addition, Patent Publication 2 discloses that a film made of an aliphatic polyester-based resin is found to have a small change in double refraction due to an external force, so that the film is suitably used as a polarized plate protection film which is usable in displays such as liquid crystal displays and plasma displays.